This invention relates to a hydraulic actuator used for a brake system, and in particular a hydraulic actuator that controls the brake pressure of an automotive wheel in order to prevent wheel locking or to apply an optimal traction to driven wheels. Many different types of hydraulic actuator for a brake system have been proposed. One such hydraulic actuator includes a housing having a hydraulic circuit through which a brake oil flows, a plurality of solenoid valves placed in respective bores formed in the housing, a motor attached on one side of the housing, and a control unit attached on the other side thereof. The control unit controls the solenoid valves and the motor so as to apply an optimized brake pressure to the wheels in accordance with the condition of the wheels. As an example, in U.S. Pat. No. 5,449,226, the hydraulic actuator includes a housing, which is made of aluminum and has an opening or a hole through which a lead line is extended. A control unit and a motor are attached to one side and opposite side of the housing, respectively. A negative terminal of the motor is connected to the housing so as to establish a connection ground. One end of the lead line is connected to a positive terminal of the motor by welding. The other end of the lead line is connected to an end portion of the control unit so that the control unit can control the motor.
In this case, welding is required to connect the positive terminal of the motor with the end of the lead line, so that it increases the ease of assembly. Moreover, when the hydraulic actuator is exposed to a severe oscillation condition, the connection of the lead between the motor and the control unit might become poor or entirely broken. Furthermore, the positive lead disposed in the opening or the hole may contact with an internal surface of the opening or hole due to the oscillation, and short-circuit.